Design Of Pulverized Coal Concentration Detection System Based On Microwave Resonator

With the rapid development of our economy,the consumption of electric energy has become an important component,and the demand for electric power has increased greatly.In recent years,our country has rapidly promoted the revolution of energy production and consumption,and in order to achieve the goal of zero carbon emission,the power system is trying to transition to zerocarbon units,represented by wind and solar power.But based on rich coal,poor oil,less gas energy resources,coal-fired power generation still plays the role of ballast,can provide an important support for the development of new energy.Therefore,it is urgent for thermal power plants to reduce coal consumption and improve boiler combustion quality and efficiency.The pulverized coal concentration of primary air in thermal power plant is one of the important parameters for safe operation of boiler,which is directly related to the combustion efficiency of pulverized coal in boiler.With the increase of combustion efficiency,the utilization ratio of coal can be increased,thus alleviating the status quo of environmental pollution.The flow of pneumatic conveying pulverized coal in primary air duct of thermal power plant is a typical sparse gas-solid two-phase flow,with the development of microwave detection technology,the measurement of solid concentration in gas-solid mixture by microwave method has become one of the hot research directions.In this paper,a resonant cavity sensor based on microwave method is used to measure pulverized coal concentration of primary air in thermal power plant.Firstly,the fundamental theory of dielectric perturbation in microwave resonator and the theory of dielectric constant of gas-solid mixture are deeply studied in this paper,the latter analyses the dielectric properties of gas-solid mixture and the influencing factors of complex dielectric.Secondly,the model of semi-open microwave cylindrical resonator is established according to the primary air duct wall,and the structural parameters are optimized by means of COMSOL simulation software,the mathematical relationship between resonant frequency and pulverized coal concentration was obtained by adding different concentration of pulverized coal to the optimized cavity.A static experimental system is designed to verify the rationality of the semiopen microwave resonator.Then the gas-solid flow field is added into the semi-open microwave resonator,and the effect of the short-circuit rod and antenna on the velocity and volume fraction of the gas-solid flow field is obtained,it is found that the gas-solid flow field affects the distribution of the electromagnetic field,and the resonant frequency shifts from 1mhz to 2mhz.The rationality and accuracy of the semi-open resonator sensor are further verified.Finally,in order to improve the detection accuracy of microwave resonator sensors.The influencing factors of pulverized coal permittivity,including temperature,moisture,and measurement frequency,were analyzed.The results show that the above influencing factors have little influence on the accuracy of the sensor.Microwave cavity sensors maintain high accuracy despite the above factors.